Revealing the fast atomic motion of network glasses

Abstract

Still very little is known on the relaxation dynamics of glasses at the microscopic level due to the lack of experiments and theories. It is commonly believed that glasses are in a dynamical arrested state, with relaxation times too large to be observed on human time scales. Here we provide the experimental evidence that glasses display fast atomic rearrangements within a few minutes, even in the deep glassy state. Following the evolution of the structural relaxation in a sodium silicate glass, we find that this fast dynamics is accompanied by the absence of any detectable aging, suggesting a decoupling of the relaxation time and the viscosity in the glass. The relaxation time is strongly affected by the network structure with a marked increase at the mesoscopic scale associated with the ion-conducting pathways. Our results modify the conception of the glassy state and asks for a new microscopic theory.

X-Ray Photon Correlation Spectroscopy Reveals Intermittent Aging Dynamics in a Metallic Glass

“…of a unique stress-dominated dynamics characterized by subsequent aging regimes: a fast exponential growth for short waiting times, followed by a long, almost stationary regime. The latter has been observed also in network glasses [13] and is contrary to the steady slowing down of the dynamics during aging observed in macroscopic studies.Here, we investigate the atomic motion in a Pd 43 Cu 27 Ni 10 P 20 MG ribbon using XPCS and show that this system ages in a highly heterogeneous manner, consisting of quiescent periods of stationary dynamics interspersed with cooperative, avalanche-like structural rearrangements. Our findings suggest the existence of a complex dynamical scenario occurring at the atomic arXiv:1509.00687v1 [cond-mat.mtrl-sci] 2 Sep 2015…”

“…The latter has been observed also in network glasses [13] and is contrary to the steady slowing down of the dynamics during aging observed in macroscopic studies.…”

Thermometer Effect: Origin of the Mixed Alkali Effect in Glass Relaxation

“…The structural origin of the MAE and glass relaxation are still regarded as one of the most challenging unsolved problems in condensed matter science [12][13][14].…”

Comparing the atomic and macroscopic aging dynamics in an amorphous and partially crystalline Zr44Ti11Ni10Cu10Be25bulk metallic glass

“…Similar results were also recently obtained during XPCS studies on a network-forming sodium silicate glass. 54 The TNM and similar phenomenological models have had broad success in describing many aspects of structural relaxation in amorphous materials, although their inadequacies have also been well documented. 40,41,51,[55][56][57][58] In the case of the XPCS experiments performed here, the failure of the TNM model is essentially due to the basic assumption that τ depends on the instantaneous state of the material via Tf.…”